Transcriptional and post-transcriptional regulation of CARMN and its anti-tumor function in cervical cancer through autophagic flux blockade and MAPK cascade inhibition.

Background: LncRNAs play essential roles in multiple tumors. However, research on genome-wide lncRNA alterations and their functions in cervical cancer (CC) is limited. This study aims to explore key lncRNAs in CC progression and uncover the molecular mechanisms involved in the development of CC.

Methods: In this study, we analyzed 30 tissues from CC, cervical intraepithelial neoplasia (CIN), and normal (NOR) using transcriptome sequencing and weighted gene co-expression network analysis to establish gene modules related to the NOR-CIN-CC transition. Machine learning diagnostic models were employed to investigate the role of lncRNAs in this transition. Molecular biological experiments were conducted to elucidate the potential mechanisms of CARMN in CC, with a particular focus on its transcriptional and post-transcriptional regulation of abnormal expression in CC.

Results: CARMN was identified as a hub gene in two modules significantly associated with the NOR-CIN-CC transition. Analysis using ten machine learning models confirmed its critical role in this progression. The results of RNA-seq, qPCR and RNAScope performed in another cohort of 83 cervical tissues all showed that CARMN was significantly downregulated in CC. CARMN significantly enhanced the interaction between Keap1 and Nrf2, leading to increased ROS levels. The elevated ROS levels suppressed the Akt/mTOR signaling pathway, leading to autophagy arrest via autophagic flux blockade. Additionally, CARMN interacted with TFAP2α to repress MAPK13 transcription, further inhibiting the MAPK cascade. A promoter SNP (rs12517403) was found to increase CC risk (OR = 1.34, 95% CI = 1.11-1.61) and reduce CARMN expression by decreasing SP1 binding. Furthermore, the RNA binding proteins that could modulate CARMN RNA stability were also determined using RNA-pulldown assay. The results demonstrated that YBX1, a component of the coding region instability determinant (CRD)-mediated mRNA stabilization complex, promoted CARMN RNA stability. DHX9, another component of complex, acted as a scaffold to bridge YBX1 and CARMN.

Conclusions: CARMN exerts an anti-cancer effect in CC progression by inhibiting the Akt-mTOR and MAPK signaling pathways. rs12517403 and the YBX1/DHX9 complex are key mechanisms influencing its transcription and stability in CC cells. CARMN represents a promising biomarker for CC diagnosis and therapeutic target.